I am using a 3X from Clear Air Tools. It works quite well and drives any rivet on the kit.
When extra money comes available (I just ordered my wings) I plan on getting a Sioux 2X just for setting 426-3 skin rivets. Not that the 3x is too much for it, just for the experience. They say the 2X can do the job with more finesse.
My advice, get a 3X first. If you never buy another gun, so be it.
Oh, and one other thing... you don't need ALOT of tools, just the right ones.
If you buy good ones from the start, you won't be disappointed.

CJ